Originally Posted by canopus27

I don't think you're holding anyone else up, the advice is not to block or delay the boarding process for others - you simply stand aside and let other people board.

The worst risk is that you'll lose overhead bin space, and the impact of that is really dependent on how much luggage you have.

The question to ask the gate agent, is whether or not the J cabin has *boarded* full. You can explain that you're waiting to see if there are any no-shows. Once J has fully boarded, there's no point delaying your own boarding any further.